Acrylic triblock copolymers, their preparation and their application to the manufacture of elastomeric articles

Abstract

Triblock copolymers containing a copolymer having a number-average molecular weight of from 3,000 to 300,000, a molecular weight polydispersity of from 1.05 to 2.0, and an A-B-C structure in which each of the blocks A and C may be a monomer sequence chosen from an acrylic, a vinylaromatic, a methacrylic or a maleimide monomer, and block B may be a monomer sequence chosen from an acrylic, a vinylaromatic or a methacrylic monomer, where at least one of the blocks A and C is different than block B.

We claim: 
     
       1. A triblock copolymer comprising: a copolymer which has a number-average molecular weight ranging from 3,000 to 300,000 and a molecular weight polydispersity ranging from 1.05 to 2.0, and an A-B-C structure in which each of the blocks A and C denotes a monomer sequence chosen from an acrylic, a vinylaromatic, a methacrylic or a maleimide monomer, block B denotes a monomer sequence chosen from an acrylic, a vinylaromatic or a methacrylic monomer, wherein at least one of the blocks A and C is different than block B.   
     
     
       2. A triblock copolymer according to claim 1, wherein blocks A and C are of identical types of monomer sequences. 
     
     
       3. A triblock copolymer according to claim 2, wherein block B represents from 10 to 99% by weight of the total copolymer. 
     
     
       4. A triblock copolymer according to claim 3, wherein block B is an acrylic monomer sequence, block A is a methacrylic monomer sequence and block B represents from 50 to 85% by weight of the total copolymer. 
     
     
       5. A method of using a triblock copolymer according to claim 4 for the manufacture of elastomeric articles. 
     
     
       6. Process for the preparation of a triblock copolymer according to claim 1, comprising: (1) conducting an anionic polymerisation of at least one monomer A with the aid of an initiating system of (i) at least one monofunctional initiator of formulas:   (R).sub.p --M                                              (I)        in which: M denotes an alkali or alkaline-earth metal,   P denotes the valency of the metal M, and   R denotes a straight- or branched-chain alkyl radical containing 2 to 6 carbon atoms, or an alkyl radical containing 1 to 6 carbon atoms, substituted by at least one phenyl group, and   (ii) at least one ligand of alkali or alkaline-earth metal salts, to obtain a living chain unit A - , then   (2) reacting said living chain unit A -   with at least one monomer B to obtain a living diblock copolymer (A-B) - , then     (3) reacting said copolymer (A-B) -   with at least one monomer C to form a living triblock copolymer (A-B-C) - , and finally   (4) reacting the copolymer (A-B-C) -   with at least one protolytic compound whereby a triblock copolymer according to claim 1 is produced.     
     
     
       7. Process for the preparation of a triblock copolymer according to claim 2, comprising: (1) conducting the anionic polymerisation of at least one monomer B with the aid of an initiating system of at least one difunctional initiator and at least one ligand of alkali or alkaline-earth metal salts, to obtain a living polymer  -  B - , then   (2) reacting said polymer  -  B -   with at least one monomer A to form a living triblock copolymer  -  (A-B-A) - , and finally   (3) reacting the copolymer  -  (A-B-A) -   with at least one protolytic compound whereby a triblock copolymer according to claim 2 is produced.     
     
     
       8. Process according to either claim 6 or claim 7, wherein the ligand is employed in a molar ratio ranging from 0.3 up to 15 to the initiator. 
     
     
       9. Process according to one of claims 6 to 8, wherein the polymerisation takes place in the presence of at least one solvent. 
     
     
       10. Process according to claims 6 to 9, wherein the polymerisation takes place at a temperature of -78° C. to +20° C.